HVAC AIR DUCT LEAKAGE
ISSUE:
Leakage testing of HVAC air ducts.
BACKGROUND:
VA Master Construction Specification Section 15840 `Ductwork and
Accessories' requires contractors to fabricate and install ductwork as
per SMACNA (Sheet Metal and Air Conditioning Contractors National
Association). However, in many cases contractors fail to meet this
standard and result in excessive air leakage.
DISCUSSION:
Excessive air leakage affects system performance as well as energy
consumption. Therefore, excessive leakage must be controlled. SMACNA
states " The need to verify leakage control by field testing is not
present when adequate methods of assembly and sealing are used.
Leakage tests are an added expense in system installation. It is not
recommended that duct systems constructed to 3 inches w.g. class or
lower be tested since it is generally recognized as being not cost
effective. For duct systems constructed to 4 inches w.g. class and
higher, the designer must determine if any justification for testing
exists. If it does, he must clearly designate in the contract
documents the portions of the system(s) to be tested and he must
specify appropriate test methods".
However, DOE 10 CFR Part 435 requires "Ductwork designed to operate at
static pressure difference greater than 3 inches w.g. shall be leak
tested and conform with HVAC Duct Leakage Manual by SMACNA. Leakage
testing may be limited to representative sections of duct system but
in no case shall be less than 25% of the total installed duct for the
designated pressure class." VA is required to meet DOE 10 CFR Part
435 "Energy Conservation Voluntary Performance Standards for
Commercial and Multi-Family High Rise Residential Buildings; Mandatory
for New Federal Buildings; Interim Rule". VA Master Construction
Specification Section 15840 was revised to meet this requirement.
RECOMMENDATION:
1. Follow duct sealing, air leakage criteria, and air leakage tests
requirements stated in VA Master Construction Specification Section
15840.
FOR ADDITIONAL INFORMATION:
Contact Satish Sehgal at 202-565-5032 in the Standards Service (187C).
19 January 1999
FM-187C-DA96
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